Fuel fired vacuum furnace



July 16,194& u. J. TURlN ET AL FUEL FIRED VACUUM FURNACE Filed Nov. 30,1944 Peter' Patented July 16, 1946 FUEL FIRED VACUUM FURNACE John J.Turin, West Newton, Mass., and Arthur W. Peters, Toledo, Ohio,assignors, by mesne assignments, to surface Combustion Corporation,Toledo, Ohio, a c'orporation' of Ohio Application November 30, 1944,Serial'No.-.565,936

8 Claims. 1

The present invention relates to the manufacture of metallic magnesiumby the thermal reduction of magnesium oxide and more particularly to animproved vacuum furnace for use in connection with such manufacture.

In the ther-mal reduction of magnesiumoxide with a reducing agent likeferrosilicon, it is customary to form the reacting ingredients intorelatively small briquettes and then to heat these briquettes toreducing temperature in a vacuum.

Heretofora'in the case of fuel fired furnace s, it has been customary toeffect the reduction of the' magnesium oxide on externally-heated,vacuum-tight retort. However, the upper temperature limit of the retorthas been only about 2100- 2150 F. due to the retort beingmade of` a hearesisting alloy (a chrome nickel iron alloy) which at said temperature'is 'semi-plastic and readily deformable. At a temperature of 2100-2150F. there is required some hours to effeot satisfactory reduction of themagnesum oxide whereas'at a temperature of only a few hundred. de'greeshigher, reducton can be efiected more' completely and in substantiallyless time.

'The present invention has for its object to provide a fue] firedfurnace which shall make it possible to heat the 'said briquettes ofmagnesium oxide containing material to reducing 'temperature without theuse of an 'externally fired vacuum-tight retort and Withal to permitsuch heating to be effected more speedily and efiiciently than hasheretofore been possible with fuel fired apparatus. Other related objectwill more fully appear hereinafter.

v For a consideration of what' we believe to be novel and our invention,attention is directedto the following specification and the claimsappended thereto.

In the drawing: r

Fig. 1 is a vertical sectional view with parts in elevation of a furnaceembodying the present invention. r u 4 Fig. 2 is a horizontal sectonalview on line '2-2 of Fig. 1. i

The improved furnace comprise's a Vacuumtight exterior metal shell or.casing 2 comprised of lower and upper portions ?a and 2b respectively,the shell having an interier lining 'I of heat insulating material. Thetop of the oasing hasa central opening encompassed by` a collar Zc, thisopening being normally closed vacuumtight by a cap type closure Sadaptedto seat on said collar. r

An internally cooled cylinder 6 depends from the closure 3 the pipewhich delivers cooling me- V dium. to the-cylinder being indioated at6a..'I'he purpose of thiscylinder 6 is to serve-as a con-` denser formagnesium vapor comingf.rom the reducing zone of the furnace presently.described.

A ball of the condensed magnesiumisindicated in broken lines at M. v i

To facilitate handling of theload constituted by the. closure 3 and.the-parts .Suspended .therefrom the closure is hung on anarm 36-01athorizontally disposed beam affixed to..anv elevator post' 31 mountedin a.support 38- securedLtothe exterior 'shell of the furnacel Anhydraulic cylinder for raising and lowering the-post 31isdiagrammatically indioated. .atr39. A spare closure 3a withcondensercylinder 6' attached is hung` the retort 20 through the top aperture ,li, it being understood that the briquettes will first have been dumpedinto the drum 9 before the closure 3 is in`p1acef Before being dumpedinto the drum 9 the briquettes will have been `preleated to atemperature of 'about'1200-1300 F. for the purpose of drying anddegasifying the same. To permit the briquettes to be temporarily held inthe drum s 9 until the retort 20 has been made fully ready to receivethem, there is provided above the aper r tur'll a stopper l 2 adaptedytobe operated by a rod' l3 extending upwardly therefrom to an op; eratinglever'M. 'A hood`l6 above the stopper prevents jamming'of the stopper bythe briquettes thereabove. The hood'is held in fixed position by'radial'struts 16'. In thedrawing; the stopper is shown in down or' closedposition. i The lever |4 is connected to' avacuum-tight Operating'device I5 outside of the'furnace shell.

The'lower end of' the drum 9 rests'on the top wall IO of the retort'25`and its upper end is" slidably 'centere'd in the collar 2c. Theunderside of theclosure 3 is protected 'against overheating by acircular body 3' of heat insulating material carried thereby and adaptedto project a short distance into the drum 9. body :permit's freemovement of the rod l3. Ex tending-laterally from the collar 20 is acondut 5 which serves to connect the interior ofthe; fur

A `vertical groove in said u nace to a source of vacuum such as a vacuumpump. i i i The bottom of the furnace shell or casing 2 has a centralopening encompassed by a collar 2d,

this opening being normally closed vacuum-fight by a closure 4 adaptedto seat on the collar. A cylinder 4' of heat insulating material'on theclosure closes the bottom of the retort. To permit'a 'waste receivingcar to be d'sposed beneath the furnace, the latter is mounted on stand-"ards 35. i v 3 To facilitate handling of the load constituted by theclosure 4, the closure is mounted on an arm 3| of a horizontallydisposed ,beam affixed'to an elevator post 32 mounted in a support 33 affixed to the furnace casing An hydraulic cylinder for raising andlowering the post is diagrammatically indicated at 34. A spare closure4a is' bottom walls the retort is preferably comprised of acircumferential series of intercomn unicatipg i relatively narrowupright Channels !8, four such channel being shown. it being understoodthat briquette's dum ed into the retort will fill these channels.thereby substantially reducing thehorizontal distance that heat musttravel radially inward to reach the center of the charge.

The retort 20 is surrounded by a refractorv structure 8 comprising anouter'circula'rwall j|9 spaced from' the retort to form a firing orcombustion space about the retort. This structure 8 is preferably madeof silicon carbide. and is 'so massive that after it has been heated. toa temperature of about 2700 F. it will contain enough heat not only toheat the charge of briquettesin the retort to reducing temperature butalso to sustainthe endothermic reaction fort a period long enough toefie'ct substantially complete reduction of the magnesium oxide.

A burner 22 is positioned in the furnace wall to fire 'tangentially into,said firing space 40 whereby to heat said structure `8 tothe'saidelevated temperature, it being understood that this firingiisdone only when -atmospheric pressure prevails within the furnace casing2 and that the burner will be shut off vacuum-tight when 'a vacuumprevails in said furnace. `ln l 'iggz, the fuel supply pipe for theburner is indicated' at 23, the same being provided with a vacuum-tightshut-off valve 24. The burners may be lighted by inserting atorchthrough a lighting' passage 25 which is normally closedvacuum-fight by'a clc sure 25'. Thewaste heating gases fiow'from thecombustion space 40 through a lateral port 28 to a waste gas fiue 27which is normally'closed vacuum-tight by a closure 29. As shown inFig.1, the firing space 40 is preferably divided into a vertical series ofcommuni cating compartments by hori'zontally disposed reractory spacers-21, each having an aperture 2l' so arranged with respect to theaperture in the next adjacent'spacer that the fiaming fuel from theburner 22 must necessarily flow in 'a circuitous path in flowingupwardly to the waste gas fiue 21. Although only one burner has beenshown, it' will be readily understood that there maybe a'vertical r owof such burners. As shown r' in Fig. 1, the'inner face of the'wall 9between adapted for its intended purpose.

e cumferential series of relatively'narrow upright- 4 the spacers 2| ispreferably serrated to more readily absorb heat from the flaming fuel.

The mode of operation of the improved fumace may be briefiy summarizedas follows: The refractory structure 8 is' heated to a temperature, ofabout 2700 F. before a vacuum prevails in the firing space 40' or, inother words, before a Vacuum prevails within furnace shell or ca'sing 2.Breparatory to producing a vacuum within the furnace the bumer 22 must,of course, be shut off vvacuum-tight. Also a charge of preheatedbriquettes Will have been dumped into the drum or barrel 9 in the upperpart 'of the furnace preparatory to being dumped into the retort 20 assoonas the bottom closure 4 is in place and ?the furnace is otherwiseready to be evacuated. As soon as the briquettes have been dumped intothe furnace the furnace is made yacuum-tight and the vacuum pumpstarted. Heating up of the removal'of the top closure 3 to permitremoval of i the condensed magnesium from the condenser 6; The furnaceis then again made ready `for another charge by reheating the structure8 a's will now be readily understood. In the meantime, the

'bottom closure 4 is removed to permitthe 'spent charge of briquettes inthe retort to drop out of the furnace into a waste receiving car beneaththe furnace. p

From the foregoing it will be seen that' the present invention providesa relatively simplegand practical fuel fired vacuum furnace which iswell The present application is a continuation 'in part of ourapplication Serial No. %55,260 filed August 18', 1942. i

What is claimed as new is: 1. In appa'ratus for the thermal treatment ina vacuum of a magnesium oxide containing material capable of evolvingmagnesium vapor, 'the e ccmbination which comprises a relatively tallheat conducting refractory structure defining a container for a chargeof said material, the said structure being chambered to provide acombustion space, burner means for delivering fuel to said combustionspace for heating said structure to an elevated temperaturesubstantialiy higher than 2100 F. before producing a vacuum' in saidreentrant channels for the reception of thesaid material.

2; In apparatus f or the thermal treatment of material under vacuum, thecombination which 'compries a'refractory structure defining a non-Vacuum tight container wherein a charge of said material will be placedfor heating to treating temperature, a vacuum-tight casing wherein saidstructure is housed and wherein a vacuum must prevail in order that a,vacuum may prevail in said container, said refractory structure being somassive that when it has been heated to an elevated temperaturesubstantially higher than the said treating temperature there will bepresent in said structure all of the heat required to maintain saidcharge at the said treating temperature, the said structure beingchambered to provide a combustion space about-the 'said container, andburner means for delivering fuei to said combustion space forheatingsaid structure'- to said elevated temperature before producing a vacuumin said casing.

3. In apparatus for the thermal treatment of material under vacuum, thecombination which comprises a reiativelytall refractory structuredefining an open top container wherein a charge of said material will beplaced for heating to' treating temperature, a vacuum-tight casingwherein said structure is housed and wherein a vacuum must prevail inorder that avacuum may prevail in said container, said refractorystructure being so massive that when it has been heated to an elevatedtemperature substantially higher than the said treatirg temperaturethere' will be present in said structure all of the heat required tomaintain said charge at the said treating temperature, the saidstructure being chambered to provide a combustion space about the saidcontainer, and burner means for delivering fuel to said combustion spacefor heating said structure to said elevated temperature before producinga vacuum in said casing.

4. In apparatus for the thermal treatment of material under vacuum, thecombination which comprises a relatively tall refractory structuredefining an open top container wherein a charge of said material will beplaced for heating to treating temperature, a vacuum-tight -casingwherein said structure is housed and wherein a vacuum must prevail inorder that a vacuum may prevail in said container, said refractorystructure being so massive that when it has been heated to an elevatedtemperature substantially high er than the said treating temperaturethere will be-present in said' structure all of the heat required tomaintain said charge at the said treating temperature, the saidstructure being chambered to provide a combustion space about saidcontainer, burner means for deiivering fuel to said combustion space forheating said structure' i vacuum of material capable of evolvingmagnesium vapor, the combination which comprises a r perature there willbe present in said structure ail of the heat required to maintain saidcharge e at the said 'treating temperature, the said structure beingchambered to provide a combustion space about said container, burnermeans for delivering fuel to said combustion spacefor heating saidstructure to said elevated temperature before producing a vacuum in saidcasing, and means {6. In apparatus for the thermal treatment'in arefractory structure defining a non-vacuum tight container for a chargeof said material, the said structure being chambered to provide acombustion space about said container wherein fuel may be burned forheating said structure to an elevated temperature of about 2700 F.before producing a vacuum in said container, burner means fordeliverngsaid fuel to said combustion space, a vacuum casing wherein saidstructure is housed and wherein a vacuum must prevail in order that avacuum may prevail in said container, said refractory structure being somassive that when it has been heated to said elevated temperature therewill be present in said structure all of the to said elevatedtemperature before producing a ing a relatively tall non-vacuum tightcontainer :r

wherein a charge of said material will be placed for heating to treatingtemperature, a vacuumtight casing wherein said structure is housed andwherein a vacuum must prevail in order that a vacuum may prevail in saidcontainer, said refractory structure being' so massive that when it hasbeen heated to an elevated temperature substantially higher than the'said treating tem heat required to maintain the said charge at manesium-evolving temperature, and means in said apparatus for condensingthe magnesium vapor evolving from said charge. v

7. In apparatus for the thermal treatment in a vacuum of a magnesiumoxide containing material capable of i evolving magnesium vapor, thecombination which comprises a relatively tall heat conducting refractorystructure defining a container for a charge of said material, the saidstructure being chambered to provide a combustion space about saidcontainer wherein fuel may be burned for heating said structure to anelevated temperature substantially higher than 2100 F. before producinga vacuum in said chamber, burner means for delivering said fuel to saidcombustion space, a vacuum casing wherein said structure is housed andwherein a vacuum must prevail in order that a vacuum may prevail in saidcontainer during the thermal treatment of said material, said structurebeing so massive that when it has been heated to said elevatedtemperature there will be present in said structure all of the heatrequired to react the charge of said material in saidcontainer.

8. In apparatus for heat treating material in a vacuum, the combinationwhich comprises a refractory structure defining a container for saidmaterial, the said structure being chambered to provide a combustionspace about said container wherein fuel may be burned for heating

